1. Field of the Invention
The present invention relates generally to stator winding and, more particularly, to an apparatus and method for forming wound coils on stators for dynamo-electric machines, including an improved drifting tool for displacing wire located in stator slots during the winding operation.
2. Description of the Prior Art
Field winding coils for stators are generally placed on the radially inwardly extending teeth of a stator by either preforming the coils and then pressing the preformed coils over the stator teeth, or by winding the coils directly onto the stator teeth. In the process where the coils are preformed, the coils are pushed onto the stator by a coil pusher which forcibly pushes the coils over the teeth of the stator, and a forming tool, or forming tools, may be provided to shape the wire in the stator slots and around the ends of the teeth in order to compactly position the coils on the stator. In such a construction, excess wire must be provided for the preformed coils in order to accommodate the necessary distortions of the coils as they are pressed over and around the stator teeth. Accordingly, such a construction has been found to provide an inefficient amount of wire, as well as result in a larger stator dimension as a result of the excess coil wire extending around the end faces of the teeth for the stator.
In the alternative construction for field winding, wire is fed from a winding spindle or tool directly onto a stator wherein the wire is successively wound around the stator teeth, and the efficiency of the winding operation is substantially dependent upon the ability to direct the wire to desired locations on the teeth as it is fed from the winding spindle. Such a device for feeding wire onto the stator to form the coils directly thereon is disclosed in U.S. Pat. No. 5,964,429, which discloses a winding tool which is supported for reciprocating and rotating movement relative to a stator. The winding tool includes a plurality of forming racks which are adapted to move radially outwardly from the winding tool in order to press the end portions of the coil windings radially outwardly and thereby facilitate placement of additional wire within the slots of the stator.
When the wire being wound into the stator slots is of a relatively thick gauge, such as in the range of 15 gauge wire, particular problems arise in the feeding and formation of wire coils on the teeth of the stator. In particular, such thick gauge wire does not typically readily conform to the contour of the slot such that the slot fill provided by thick gauge wire may be reduced relative to thinner more flexible gauges of wire.
Further, unique problems relating to feeding of the wire arise with thicker gauges of wire in that such wire is subject to cold working and/or kinking, both of which may adversely affect the character of the coil windings for the stator.
The present invention provides an apparatus and method for winding wire into the slots of a stator, and in particular provides a method and apparatus which effectively feeds thicker gauge wire to desired locations on the stator to thereby form field coils, and to provide such field coils to the stator with higher slot fills as compared to prior art methods and apparatus.
In one aspect of the invention, an apparatus is provided for forming field coils on a stator for a dynamo-electric machine wherein the apparatus includes a stator mount for supporting a stator, a winding tool supported for reciprocating movement relative to the stator mount and including a wire feed passage for feeding wire into the slots of the stator, a drifting tool located adjacent a longitudinal end of the winding tool and supported for reciprocating movement with the winding tool. The drifting tool includes at least one drifting blade extending radially outwardly for passing through a slot in the stator supported in the stator mount whereby the drifting blade engages wire in the stator slot to thereby displace the wire within the slot and provide clearance for additional wires on successive passes of the winding tool through the stator as well as to ensure that the wires comprising completed coils are compactly formed.
In another aspect of the invention, an upper wire retainer is provided and is supported for movement toward and away from the upper end of the stator to engage cross-over wires extending between coils formed on the stator. The upper wire retainer includes a finger structure extending radially inwardly and terminating in downwardly extending tangs which are configured to be located overhanging the radial outer edge of the stator slots.
A lower wire clamp is also provided located on the winding tool beneath the stator. The lower wire clamp includes a clamp member which is slidably movable relative to the winding tool and which is spring biased toward the lower end of the stator. The lower wire clamp engages the lower end turns of wire coils on the stator in response to upward movement of the winding tool to hold the end turns from displacing radially inwardly toward the center of the stator.
In a further aspect of the invention, the winding tool is formed of a plurality of winding tool parts including a wire guide base, a wire guide cap cooperating with the wire guide base to form passages for wire to pass through the winding tool, and a cylindrical winding tool sleeve surrounding the wire guide base and wire guide cap. The winding tool sleeve includes wire exit apertures for feeding wire from the winding tool radially outwardly into the slots of the stator.
The wire guide base and wire guide cap define a portion of a wire feed passage passing through the winding tool, and in particular define a plurality of downstream, branch passages extending from an upstream, main passage of the wire feed passage. The branch passages each guide an individual wire from the main passage to a wire exit aperture on the winding tool sleeve. The branch passages are separated from each other by passage walls and the passage walls have a thickness, at an interface between the main passage and the branch passages, which is less than the width of the branch passages. Wires passing through the main passage toward the branch passages are separated from each other at the interface between the main passage and the branch passages whereby the leading ends of the wires are automatically directed to a respective branch passage as they pass from the main passage. Accordingly, the wire guide base and wire guide cap form a structure for facilitating self threading of the wire through the winding tool.
In a further aspect of the invention, a wire feed mechanism is provided for feeding wire to the wire feed passage. The wire feed mechanism comprises a wire feed plate including a drive belt and a wire drive pulley in engagement with the drive belt wherein the wire drive pulley includes a groove for receiving wire therein to thereby maintain the wire in engagement with a predetermined portion of an outer surface of the wire drive pulley. A wire exit member is provided at a pick-up point along the wire drive pulley and includes a wire pick-up lip extending into the groove for engaging wire located therein and directing the wire toward the wire feed passage. Accordingly, the wire exit member provides a mechanism for self threading the wire fed from the wire feed plate into the wire feed passage, and it can therefore be seen that the apparatus of the invention provides for self threading of the wire through the apparatus from the wire feed mechanism through to the wire exit apertures on the exterior of the winding tool.
Other aspects of the invention will be apparent from the following description, the accompanying drawings and the appended claims.